The fundamental bases involved in the immunological regression of line-10 hepatomas in strain 2 guinea pigs are the principal concerns of this project. The roles of various microbial components, such as trehalose mycolates (P3), mycobacterial cell walls and endotoxin, in stimulating this immune response are evaluated. Also investigated is the role of P3 in complexing the essential protein antigen to minute oil droplets so that cell-mediated immunity is principally stimulated against the line-10 cancer.